The key word is “safely”. This kind of investment would be considered high risk—this company only started this program three years ago, and the first trees haven’t yet produced profit. Additionally, the 10 year duration is unattractive for many investors, and there isn’t really a market for this type of wood in North America yet. They need to offer a big reward in order to entice investors to fund their venture at this early stage.
I suspect other early stage ventures would have a similar high-risk, high potential return profile, which is why they are typically limited to accredited investors.